An experimental stroke model in the Rhesus monkey has been developed. The "stroked" animals are being evaluated by X-ray angiography, radionuclide scanning, radionuclide cerebral blood flow determination, radionuclide particles (macroaggregates) transit, fluorescein angiography, microangiography, and autoradiography. The CBF in the experimental infarcted brain is being modified by various physiological, chemical, pharmacological and surgical (revascularization) means. In a collateral experiment various parameters of the cerebral circulation are being studied after production of arterial spasm in the circle of Willis in monkeys. The spasm is caused by total blood or fractions thereof introduction within the subarachnoidal space (chiasmatic cistern).